Python

Build WebAssembly plugins using Python. Noorle uses componentize-py to compile Python to WASI Preview 2 WebAssembly.

Setup

Install Tools

# Install Noorle CLI
curl -L cli.noorle.dev | sh

# Create a new Python plugin
noorle plugin new my-python-plugin --lang python
cd my-python-plugin

Project Structure

my-python-plugin/
├── src/
│   ├── __init__.py           # Entry point
│   ├── tools.py              # Tool implementations
│   └── utils.py              # Utilities
├── tests/
│   └── test_tools.py
├── pyproject.toml            # Dependencies
├── noorle.yaml               # Plugin config
├── world.wit                 # Component interface
├── .env
└── README.md

Define Tools

Tools are Python functions exported from your plugin.

Simple Function

# src/tools.py
def greet(name: str) -> str:
    """Greet a person by name"""
    return f"Hello, {name}!"

def add(a: float, b: float) -> float:
    """Add two numbers"""
    return a + b

Complex Types

from typing import Dict, List

def process_data(
    items: List[str],
    config: Dict[str, str]
) -> Dict[str, int]:
    """Process a list with configuration"""
    result = {}
    for item in items:
        key = config.get("prefix", "") + item
        result[key] = len(item)
    return result

def search_items(
    query: str,
    limit: int = 10
) -> List[Dict[str, str]]:
    """Search for items"""
    return [
        {"id": str(i), "title": f"{query}_{i}"}
        for i in range(min(limit, 5))
    ]

Type Annotations

Python type hints define the tool interface:

def my_tool(
    required_param: str,          # Required string
    optional_param: str = "default",  # Optional with default
    count: int = 1,               # Integer parameter
    items: List[str] = None,      # List type
    config: Dict[str, str] = None # Dictionary type
) -> str:                         # Return type
    """Tool description"""
    return f"Processed: {required_param}"

Supported types:

str - String
int - Integer
float - Floating point
bool - Boolean
List[T] - Array of type T
Dict[str, T] - Object with string keys
Optional[T] - Nullable type

Working with Dependencies

Add Dependencies

Edit pyproject.toml:

[project]
name = "my-python-plugin"
version = "0.1.0"
dependencies = [
    "requests==2.31.0",
    "pandas==2.0.0",
    "pydantic==2.0.0",
]

[build-system]
requires = ["setuptools", "componentize-py"]
build-backend = "backend"

Install and Build

# Install dependencies locally
pip install -e .

# Build the plugin
noorle plugin build

Size Considerations

Large dependencies increase plugin size:

# ❌ Heavy dependencies
numpy = "1.24.0"      # 30MB+ with dependencies
tensorflow = "2.14.0" # 100MB+ with dependencies

# ✅ Lightweight alternatives
statistics               # Standard library stats
decimal                  # High precision math

File I/O

Access allowed filesystem paths via environment or configuration.

import os
from pathlib import Path

def read_config() -> str:
    """Read configuration file"""
    config_path = Path("/allowed/path/config.json")
    return config_path.read_text()

def write_cache(key: str, value: str) -> bool:
    """Write to cache"""
    cache_dir = Path(os.getenv("CACHE_DIR", "/cache"))
    (cache_dir / f"{key}.txt").write_text(value)
    return True

def list_files(directory: str) -> List[str]:
    """List files in directory"""
    dir_path = Path(directory)
    return [f.name for f in dir_path.glob("*")]

Configure Permissions

In noorle.yaml:

permissions:
  filesystem:
    allow:
      - uri: "fs://cache/**"
        access: [read, write]
      - uri: "fs://config/**"
        access: [read]

  environment:
    allow:
      - key: "CACHE_DIR"

Environment Variables

Access configuration via environment variables.

import os

def get_api_credentials() -> Dict[str, str]:
    """Get API credentials from environment"""
    return {
        "api_key": os.getenv("API_KEY", ""),
        "api_secret": os.getenv("API_SECRET", ""),
    }

def get_database_url() -> str:
    """Get database URL with fallback"""
    return os.getenv("DATABASE_URL", "sqlite:///:memory:")

Configure in .env:

API_KEY=sk-1234567890
API_SECRET=secret-value
DATABASE_URL=postgres://localhost/mydb

Network Access

Make HTTP requests to allowed hosts.

import urllib.request
import json

def fetch_data(url: str) -> str:
    """Fetch data from allowed host"""
    try:
        with urllib.request.urlopen(url) as response:
            return response.read().decode('utf-8')
    except Exception as e:
        return f"Error: {str(e)}"

def post_json(url: str, data: Dict) -> str:
    """POST JSON to allowed host"""
    import urllib.parse

    json_data = json.dumps(data).encode('utf-8')
    req = urllib.request.Request(
        url,
        data=json_data,
        headers={"Content-Type": "application/json"}
    )

    with urllib.request.urlopen(req) as response:
        return response.read().decode('utf-8')

Or use requests (add to pyproject.toml):

import requests

def call_api(endpoint: str, params: Dict[str, str]) -> str:
    """Call external API"""
    response = requests.get(
        f"https://api.example.com/{endpoint}",
        params=params,
        timeout=5
    )
    return response.text

Configure network permissions:

permissions:
  network:
    allow:
      - host: "api.example.com"
      - host: "*.github.com"

Error Handling

Return errors gracefully:

def safe_operation(data: str) -> Dict[str, str]:
    """Perform operation with error handling"""
    try:
        if not data:
            return {"error": "Empty input"}

        result = process(data)
        return {"success": True, "result": result}

    except ValueError as e:
        return {"error": f"Validation error: {str(e)}"}
    except Exception as e:
        return {"error": f"Unexpected error: {str(e)}"}

def process(data: str) -> str:
    """Internal function"""
    if not isinstance(data, str):
        raise ValueError("Expected string")
    return data.upper()

Testing

Test your plugin locally before uploading.

Unit Tests

# tests/test_tools.py
import sys
sys.path.insert(0, '../src')

from tools import greet, add, process_data

def test_greet():
    result = greet("Alice")
    assert result == "Hello, Alice!"

def test_add():
    assert add(2, 3) == 5
    assert add(1.5, 2.5) == 4.0

def test_process_data():
    items = ["hello", "world"]
    config = {"prefix": "test_"}
    result = process_data(items, config)
    assert result["test_hello"] == 5
    assert result["test_world"] == 5

Run tests:

pytest tests/

Integration Tests

# Build and test the plugin
noorle plugin build
noorle plugin test my-tool --input '{"param": "value"}'

Building and Deploying

Build

noorle plugin build

# Output:
# ✓ Building plugin...
# ✓ Compiling Python to WebAssembly
# ✓ Creating my-python-plugin.npack (234KB)

Upload

noorle plugin push --api-key YOUR_KEY

# Output:
# ✓ Uploading plugin...
# ✓ Plugin ID: 550e8400-e29b-41d4-a716-446655440000
# ✓ Active version: v1
# ✓ Tools: greet, add, process_data

Best Practices

Input Validation

def validate_input(name: str, age: int) -> Dict[str, str]:
    """Validate and process input"""
    errors = []

    if not name or len(name.strip()) == 0:
        errors.append("Name cannot be empty")

    if age < 0 or age > 150:
        errors.append("Age must be between 0 and 150")

    if errors:
        return {"error": "; ".join(errors)}

    return {"success": True}

Logging

import sys

def log(message: str, level: str = "INFO"):
    """Log message"""
    print(f"[{level}] {message}", file=sys.stderr)

def my_tool(input_data: str) -> str:
    """Tool with logging"""
    log(f"Processing: {input_data}")
    result = process(input_data)
    log(f"Completed", "DEBUG")
    return result

Documentation

def transform_text(
    text: str,
    uppercase: bool = False,
    trim: bool = True
) -> str:
    """
    Transform input text.

    Args:
        text: The text to transform
        uppercase: Convert to uppercase if True
        trim: Remove leading/trailing whitespace if True

    Returns:
        Transformed text
    """
    if trim:
        text = text.strip()
    if uppercase:
        text = text.upper()
    return text

Example: Complete Plugin

# src/tools.py
import os
import json
from typing import Dict, List

def get_weather(city: str, units: str = "celsius") -> Dict[str, str]:
    """
    Get weather for a city.

    Args:
        city: City name
        units: Temperature units (celsius or fahrenheit)

    Returns:
        Weather data
    """
    import urllib.request

    api_key = os.getenv("OPENWEATHER_API_KEY", "")
    if not api_key:
        return {"error": "API key not configured"}

    url = (
        f"https://api.openweathermap.org/data/2.5/weather"
        f"?q={city}&appid={api_key}&units={units}"
    )

    try:
        with urllib.request.urlopen(url) as response:
            data = json.loads(response.read().decode())
            return {
                "city": data.get("name"),
                "temp": str(data["main"]["temp"]),
                "description": data["weather"][0]["description"],
            }
    except Exception as e:
        return {"error": f"Failed to fetch weather: {str(e)}"}

Troubleshooting

Build fails with “componentize-py not found”:

pip install componentize-py

Plugin too large (>5MB):

Remove unnecessary dependencies
Use lighter alternatives
Check import statements

Type errors during build:

Ensure all function parameters have type hints
Check return type annotations
Verify List/Dict syntax: List[str], Dict[str, int]

Getting Started

Plugin Development

Language Guides

Deployment

Setup

Install Tools

Project Structure

Define Tools

Simple Function

Complex Types

Type Annotations

Working with Dependencies

Add Dependencies

Install and Build

Size Considerations

File I/O

Configure Permissions

Environment Variables

Network Access

Error Handling

Testing

Unit Tests

Integration Tests

Building and Deploying

Build

Upload

Best Practices

Input Validation

Logging

Documentation

Example: Complete Plugin

Troubleshooting

Next Steps

Getting Started

Plugin Development

Language Guides

Deployment

​Setup

​Install Tools

​Project Structure

​Define Tools

​Simple Function

​Complex Types

​Type Annotations

​Working with Dependencies

​Add Dependencies

​Install and Build

​Size Considerations

​File I/O

​Configure Permissions

​Environment Variables

​Network Access

​Error Handling

​Testing

​Unit Tests

​Integration Tests

​Building and Deploying

​Build

​Upload

​Best Practices

​Input Validation

​Logging

​Documentation

​Example: Complete Plugin

​Troubleshooting

​Next Steps

Setup

Install Tools

Project Structure

Define Tools

Simple Function

Complex Types

Type Annotations

Working with Dependencies

Add Dependencies

Install and Build

Size Considerations

File I/O

Configure Permissions

Environment Variables

Network Access

Error Handling

Testing

Unit Tests

Integration Tests

Building and Deploying

Build

Upload

Best Practices

Input Validation

Logging

Documentation

Example: Complete Plugin

Troubleshooting

Next Steps